The use of pile driving as a method of foundation of buildings and constructions has become widespread in recent years, for example because land for building is becoming sparse in the vicinity of many large cities, and piles driven into the ground can be used to provide a strong foundation even in areas where building is otherwise not possible because of the low bearing capacity of the soil. Furthermore, the development of more efficient pile driving machines used for driving piles, and the pile driving devices of the machines, as well as the decrease in the costs caused by pile driving, have made foundations based on pile driving less expensive and thereby more competitive than before, compared with alternative foundation solutions.
A factor that has conventionally limited the use of pile driving is that driving piles into the ground by hammering causes relatively loud noise which can be found intrusive in the immediate surroundings (for example in a residential area). In noise investigations on impact pile driving devices, the noise has been found to be produced in the hammer ram of the impact pile driving device when the massive part moving back and forth in connection with the frame of the hammer ram, that is, the block, hits a pile cap placed on top of the pile, which will transfer the impact to the pile to be driven into the ground, whereby intensive momentary deformation takes place in the walls of the pile, particularly in the case of steel piles. This sudden deformation will emit pronounced pressure variation, i.e. noise, to the environment. Without noise protection, the noise level in the vicinity of the impact pile driving device may exceed 100 decibel during the impact driving of the pile into the ground (particularly in the case of steel piles). This drawback has limited the use of impact pile driving particularly in areas where the noise has a very harmful effect, such as in densely populated residential areas. Naturally, the high noise level during the use of the impact pile driving device is also harmful to the operators of the impact pile driving device and other persons working on the construction site. Because of the noise, impact pile driving is often replaced by other pile driving methods which are less effective and more expensive, and which impose a heavier burden on the environment.
When concrete piles are driven, pile cushioning is used in pile driving devices of prior art for protecting the pile head from damage. These also have some effect on the vibration of the pile and thereby the generation of noise.
For reducing the noise level, various noise suppression solutions for impact pile driving devices have been developed. The aim has been to make the structures of the hammer ram as noise suppressing as possible, and noise reducing devices, to be installed around the pile to be driven into the ground, have been developed for suppressing the noise caused by the pile. According to tests and experiments made by the applicant, the solutions developed for the hammer ram have a limited effect. The use of noise reducing devices installed around the pile, in turn, involves the drawback that the pile remains invisible within the noise reducing device, whereby the pile driving operation cannot be followed visually. Moreover, the use of such a noise reducing device requires that the device is installed around the pile each time before starting the impact driving of a new pile into the ground. Naturally, this makes the whole pile driving process slower and more complicated.